The present disclosure relates to a power supply device that generates a stable direct current voltage by rectifying an alternating current, and in particular, to a power supply device having a PFC control circuit.
Power supply devices having a PFC (power factor correction) control IC (integrated circuit) can suppress occurrence of harmonics by improving the power factor. As such a power supply device, there is a power supply device described in Japanese Unexamined Patent Application Publication No. 11-164548.
The power supply device described in Japanese Unexamined Patent Application Publication No. 11-164548 is designed to prevent an excessive current from flowing in a capacitor and a switching element from being broken due to the excessive current upon activation and a rapid rise of an input voltage when returning from an instantaneous interrupt (instantaneous stoppage of alternating current power supply) of the alternating current power supply. In Japanese Unexamined Patent Application Publication No. 11-164548, a current flows in a sensing resistor to compare the detected voltage with a reference value, and when an excessive current is detected, an output of a drive pulse to the switching element is stopped.
Typically, overcurrent limiting circuits in the past are designed to operate upon activation, overload, an abrupt change in the load, instantaneous interruption of alternating current power supply, a decrease in the voltage of alternating current power supply, and the like. In the configuration in the past, an overcurrent is commonly limited near a phase angle of 90° of the alternating current power supply, where the peak value of the current flowing in a choke coil is high. However, in a case of carrying out an abnormal condition test, the function of overcurrent limitation may not work. In that case, an overcurrent condition may occur near a phase angle from, for example, 30° to 40° of the alternating current power supply, and a problem of an increase in loss occurs, which leads to a problem of increasing electrical stress to semiconductors, such as a switching element.
In the past, for an overcurrent in such an abnormal condition, heat generation due to an increase in loss of semiconductors, such as a switching element, used to be sensed by a temperature element, and when the temperature became at a predetermined value or higher, the operation has been stopped. This method is problematic because electrical stress has been applied to a semiconductor during a period until overheating. Further, this method may not stop the operation with an increase in loss at a level not sensed as an overheat.
Accordingly, it is desirable to provide a power supply device that can carry out protection during such an abnormal condition test more securely compared to heat generation sensing.